Synthesis, structure and electrical properties of a two-dimensional organic conductor α − (BEDT−TTF) 2BrI 2

Abstract

Single crystals of α−(BEDT−TTF) 2BrI 2 were prepared using standard electrochemical techniques in nitrogen saturated benzonitrile solution containing (n-C 4H 10) 4NBrI 2 as supporting electrolyte. The crystal is found to be triclinic, space group p1̄. The most prominent intermolecular S-S contacts (the shortest one being 3.468Å) are found between the stacks of BEDT-TTF. The room temperature conductivities in ab-plane range typically between2–10 (ohm, cm) -1. The conductivity anisotropy in this plane is small with ratio of σ a σ b ≦ 2 , while in the direction perpendicular to the ab-plane show a conductivity value at least 1000 times smaller. The temperature dependence of conductivities shows that in the temperature range between265 (245) K and 300K the crystal behaves like a two-dimensional metallic conductor and a metal-insulator transition occurs at 265 (245) K.